As Melbourne watches the number of COVID-19 cases rise, infectious diseases physician Steven Tong is seeing younger patients getting "really, really sick" from the virus.

The Royal Melbourne Hospital now has three dedicated COVID wards on top of two "pods" in intensive care.

Dr Tong says he is seeing a "constant stream" of patients.

"It's pretty busy," he told Virginia Trioli on ABC Radio Melbourne.

"I guess this year is different compared to around this time last year.

Young, pregnant, unvaccinated

In 2020 COVID severely impacted older Victorians, but Dr Tong said this year his patients were generally younger and unvaccinated.

He said he had seen instances of entire multi-generational households being hospitalised.

One of his patients is a pregnant woman in her 30s who lives in Melbourne's west.

She was staying at home to avoid infection but had not been vaccinated.

One day her husband went to pick something up from the chemist and came back with COVID.

"She's now about day 15 or 16 after her initial symptom onset — halfway through that she needed to be hospitalised," Dr Tong said.

COVID can be more severe for pregnant women and in Victoria expecting mums are now eligible for priority access to vaccinations.

With the oxygen and additional treatments, the patient's condition has improved and Dr Tong hopes she will be able to return home soon.

Fit tradie in ICU

Another of Dr Tong's patients is a father of four aged in his 30s.

The tradesman's entire family, from Melbourne's west, got COVID and despite being fit he was hit hard.

"He has been in the hospital for over two weeks now," Dr Tong said.

"He was on a ventilator for about five days and in and out of intensive care.

"He is … getting better, but you know — it's touch and go.

His wife and children have been recovering from the virus at home.

The man is now urging all of his friends and family to get vaccinated.

Bracing for more

With considerable community transmission despite Victoria's tough lockdown, Dr Tong expects cases to continue to rise and ICUs to be busier than during last year's peak.

"I think it's just going to keep going," he said.

Victoria's infection numbers look like they are quickly catching up to Sydney's and Dr Tong says it is "hard to see that turning around".

"We've really just got to get those vaccination rates up to both reduce transmission and also reduce people needing to come into hospital when they do get exposed," he said.

With vaccinations, better personal protective equipment and "air scrubbers" around the ward, Dr Tong said staff felt safer than they did in 2020.

But there is a long road ahead for hospital workers.

"We are getting tired and stretched," Dr Tong said.